In colder parts of the country, March comes in like a lion. Here in California, March comes in like a duck. Days are often sunny but not so hot. Solar electricity generation levels are high, but cooling demand is low.
Ten years ago, some prescient energy analysts at CAISO were thinking about how an increase in wind and solar generation might impact grid operations on sunny-but-cool California days. They projected electricity demand net of wind and solar generation (aka “net load”) in a future with increasing solar PV penetration. These projections gave rise to a now-familiar duck:
The CAISO duck curve caught people’s attention because it brought some looming renewable energy integration challenges into clearer focus. One of these challenges lies in the duck’s growing belly. As solar PV penetration increases, net load can bump up against the minimum generation levels of other grid-connected generators. If grid operators can’t find enough demand to soak up the sun, they have to curtail the excess solar generation.
Ten years later, these once-hypothetical over-generation challenges are here for real. Spring after spring, we set new records for renewable energy curtailment. Last April, CAISO reports that a record 596,175 MWh was curtailed. That’s like producing an entire extra day’s worth of electricity in April and then throwing it away.